AFMC AFMC Solved Paper-2010

  • question_answer
    A body is executing SHM when its displacement from the mean position are 4 cm and 5 cm it has velocity 10 cms-1 and 8 cms-1 respectively. Its periodic time t

    A) \[\frac{2\pi }{2}\sec \]                                  

    B) \[\pi \sec \]

    C) \[\frac{3\pi }{2}\sec \]                                  

    D) \[2\pi \sec \]

    Correct Answer: B

    Solution :

    For a body executing SHM, velocity,\[v=\sqrt{{{\omega }^{2}}({{a}^{2}}-{{y}^{2}})}\]we have \[{{10}^{2}}={{\omega }^{2}}({{a}^{2}}-{{4}^{2}})\]and   \[{{8}^{2}}={{\omega }^{2}}({{a}^{2}}-{{5}^{2}})\] So,    1\[{{10}^{2}}-{{8}^{2}}={{\omega }^{2}}({{5}^{2}}-{{4}^{2}})={{(3\omega )}^{2}}\]or           \[6=3\omega \] or           \[\omega =2\] \[\because \]          Time, \[t=2\pi /\omega \] \[\therefore \]     \[t=2\pi /2=\pi \sec \]


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